Various implantable medical devices, such as implantable cardioverter/defibrillators and pacemakers, include wireless communication capability. This wireless communication capability allows for communication with the implantable medical device after the device is implanted within a patient. Thus, information can be provided to or obtained from an implanted medical device without requiring the patient to undergo a post-implant surgical procedure.
In an exemplary scenario, a clinician uses an external programmer placed outside the patient's body and in near proximity to an implanted pacemaker to transmit pacing mode and other operating characteristics to the pacemaker. As another example, information can be transmitted from the implanted pacemaker and received by the external programmer operating in close proximity to the pacemaker.
Various telemetry systems for transmitting to or from an implanted medical device have utilized radio-frequency energy as the transmission medium. An exemplary telemetry system for an external programmer and a cardiac pacemaker is described in U.S. Pat. No. 4,562,841 (hereinafter the “'841 patent”). The '841 patent is assigned to Cardiac Pacemakers, Inc., and the '841 patent is incorporated herein in its entirety for all purposes. A radio-frequency carrier is modulated with digital information, typically by amplitude shift keying where the presence or absence of pulses in the signal constitutes binary symbols or bits. The external programmer transmits and receives the radio signal with an antenna incorporated into a wand, which can be positioned in proximity to the implanted medical device. The implanted device also generates and receives the radio signal by means of an antenna associated with the device.
For communication to take place in typical telemetry systems, antenna inefficiencies, as well as other limitations, required placement of the wand in near proximity to and/or within a narrow alignment window. This requirement is inconvenient for a clinician or patient, and limits situations in which communication with an implanted device can take place. Thus, there is a need in the art for improved systems and methods for wireless communications with medical devices.